04.12.2023
Storing carbon in soil can help mitigate climate change. In particular, soil organic matter that is bound to minerals can store carbon over the long term. A team including researchers from the Max Planck Institute for Biogeochemistry and the Martin Luther University Halle-Wittenberg investigated which factors regulate the organic matter associated with minerals.
The study, published in the journal Global Change Biology, shows that although the formation of mineral-bound organic matter depends primarily on the mineral species, it is also influenced by land use and management intensity.
Organic carbon in soils is not only important for soil fertility and food production, but also plays a significant role in our climate: soils are the largest terrestrial carbon store and seven percent of atmospheric CO is released every year2 implemented in the ground. Many soils have already lost large amounts of carbon to the atmosphere through agricultural use.
To counteract climate change, we therefore need to understand how to prevent further losses and how to rebuild soil carbon stores. Carbon bound to minerals remains in the soil longer and is less sensitive to disturbance. The formation of mineral-bound organic matter (MAOM) is therefore a key process in the global carbon cycle. Despite decades of research, it remains unclear how soil mineral composition and other factors, such as land use and farming intensity, influence MAOM formation.
To fill this research gap, more than 3,500 permeable containers containing carbon-free minerals found in soils were buried at 150 forest and 150 grassland sites. The minerals were either the iron oxide goethite or the silicate clay mineral illite. The test sites are located in the three study regions of the “Biodiversity Exploratories” infrastructure priority program financed by the German Research Foundation (DFG) across Germany.
After five years of incubation underground, a research team led by De Shorn Bramble from the Max Planck Institute for Biogeochemistry (MPI-BGC) in Jena and Susanne Ulrich from the Martin Luther University of Halle (MLU) analyzed the accumulation of carbon on the minerals. They found that goethite accumulates four times more organic carbon than illite, regardless of land use. This result highlights that mineral composition is crucial for the rate and amount of MAOM formation in soils.
“Most of what we know about the role of oxides and silicate clay minerals, two important mineral groups in soils, comes from laboratory studies. Because these two mineral groups exist as a mixture in natural soils, it is not possible to clearly determine their role in the formation of MAOM to determine,” explains Susanne Ulrich, doctoral student at MLU.
She continues: “With our experimental setup, we were now able for the first time to directly compare the carbon storage potential of these two mineral groups under field conditions. Our results show that not only the existence and size of the mineral surface, but the respective surface properties are crucial for the formation of MAOM Therefore, oxides have a much greater potential for storing carbon than silicate clay minerals.
Because carbon is bound to minerals for a very long time, MAOM formation was assumed to be relatively insensitive to anthropogenic disturbances on timescales below decades. In their study, however, the researchers found changes after just five years: MAOM formation in forests decreases as the intensity of wood harvesting increases and it is also influenced by the tree species. In grassland, both increasing plant productivity and plant diversity promote MAOM formation. Plant productivity and plant diversity are in turn influenced by fertilization, it increases productivity but reduces diversity.
De Shorn Bramble, a doctoral student at the Max Planck Institute for Biogeochemistry, illustrates the new results: “We observed significant effects of land use and management on MAOM formation after exposing carbon-free minerals to ambient soil conditions for just five years. “These changes are likely to occur in natural soils, but are difficult to detect using traditional methods. Our experimental approach and the insights gained from it can help predict how MAOM responds to human activities.”
Finally, he notes that although mineral composition determines the carbon storage potential of soils, land use influences the extent to which this potential is realized. In order to be able to predict MAOM formation in soils even more precisely, it appears necessary to examine the interactions between minerals, the amount and chemical composition of plant residues introduced into the soil and the community of microbial decomposers in more detail in the future.
» Originalpublikation
2023-12-03 23:05:26
#factors #determine #carbon #storage #soils
